形式主语it的5种用法是什么

不定式作真正主语

主要用于下列句型：1It + is/was + adj/n(形容词或名词) +to do sth　名词从句作真正主语

用it 作形式主语的结构主要用于下列句型：It +谓语+名词从句(主语从句、表语从句、同位语从句) 1It is +名词+从句:这样的名词有a fact,a surprise,an honor(非常荣幸),a pity,common knowledge(常识)等例如：It is common knowledge that the full moon brings fair weather皓月兆天晴,这是常识It is a surprise that you gave such an answer to the question你对这个问题作了这样的回答,令人吃惊2It is +形容词+从句:这样的形容词有natural,true,strange,necessary,important,obvious(很明显),certain,wonderful,funny,possible,likely,probable等例如：It is certain that free medical care will be given to most people in our city我们城市的多数人将享受免费医疗,这是一定的It is probable that he has known everything很可能他什么都已经知道了3It +动词+从句:这样的动词有seem,happen,appear,look,matter,make,strike,occur(突然想起)等It appeared that he had a taste for music看来他对音乐有一定的鉴赏力It made us very happy that she was saved她能化险为夷令我们大家很高兴4It + be + 分词+从句:这样的分词有 said(据说),reported(据报道),believed(人们相信),known(众所周知),decided(已决定),proved(已证实),thought,expected,annouced,arranged,amusing,puzzling,striking等例如：It is said that Li Hao has been to Europe据说李郝去过欧洲It was amusing that a rabbit ran out of the empty box on the desk桌上的空盒子里竟然跑出来一只兔子,太有趣了需要说明的是,大部分连接词引导的主语从句都可以用 it充当形式主语例如：It remains unknown when they are going to get married他们何时结婚依然不明It says in the newspaper that the enemy has been defeated报纸上报导敌人被打败了形式主语：It +be+(the)+adj+for sb+to do sth

“it”引导主语从句和“it”做形式主语还有强调句型的区别：

it引导的主语从句，形式主语就是it，真正的主语在句子的后面，通常是to do的不定式短语。

而强调句的结构 it is/was+被强调部分+that/who+句子其余部分，结构词it is/was和that/who都是没有实际意思的，只是构成句子结构的词而已。这个强调句只能强调名词和代词，也就是主语和宾语，不能强调其他句子成分。

主语从句：It is kind of you to help me with my housework

强调句：It is you who help me with my housework

主语从句中it做形式主语的常见句型：

It + be + 形容词+主语从句，如：It is uncertain whether he can come to Jenny’s birthday party or not

It + be + 名词词组 + 主语从句，这类名词有：a fact, a pity, a shame, an honour，a question等，如：It’s a pity that you missed the exciting football match

It remains a question whether he will come or not

It + be + 过去分词+ 主语从句，这类过去分词有：announced, believed, expected, hoped, decided, reported, said, shown等，如：It is reported that 16 people were killed in the earthquake

本文中，我为大家整理了形式主语it的5种用法，快来看看吧！

it的5种用法

1、指代性it一般是指人称代词it，it作人称代词时可指代事物、动物、婴儿、未知的人或一件事。

2、不定式作主语，It's my pleasure (to help you)

3、it做先行词。

4、it做形式宾语。

5、引导强调句的it。

it做形式主语基本句型

1It+be+形容词+主语从句，如：It is uncertain whether he can come to Jenny’s birthday party or not

2It+be+名词词组+主语从句，这类名词有：a fact,a pity,a shame,an honour，a question等，如：It’s a pity that you missed the exciting football match It remains a question whether he will come or not

3It+be+过去分词+主语从句，这类过去分词有：announced,believed,expected,hoped,decided,reported,said, shown等，如：It is reported that 16 people were killed in the earthquake It is not decided who will give the operation to the patient

4It+不及物动词(seem,appear,happen等)+主语从句,这类不及物动词有：appear,happen,seem等，如：It seemed that he didn’t tell the truth  It happened that I was out when he called

5It+be+形容词+for sb）+动词不定式这类句型常用形容词easy,difficult,hard,important,possible，wise等作表语，有时候为了强调不定式动作的执行者，常在不定式前加for sb，如：It’s necessary for the young to master two foreign language It is unwise to give the children whatever they want  这类形容词有：easy, difficult, hard, important, possible，wise

1It is/was + 被强调部分 + that/who  该句型是强调句型。被强调部分可以是主语，宾语，表语或状语。强调的主语如果是人，that 可以由 who 换用。如果把这种句型结构划掉后，应该是一个完整无缺的句子。这也是判断强调句型与其它从句的方法。

一般陈述句：Tom bought a book in this bookshop yesterday

It is Tom who/that bought a book in this bookshop yesterday  强调主语

It is a book that Tom bought in this bookshop yesterday      强调宾语

It is in this bookshop that Tom bought a book yesterday      强调地点状语

It is yesterday that Tom bought a book in this bookshop      强调时间状语

2 It is not until + 被强调部分 + that  该句型也是强调句型。主要用于强凋时间状语，译成汉语 “直到……才……”，可以说是 not until 的强调形式。 

It was not until she took off her dark glasses that I realized she was a famous film star 强调句

= Not until she took off her dark glasses did I realize she was a famous film star  倒装句

= I didn't realize she was a famous film star until she took off her dark glasses  一般句式

3 It is+形容词（clear /obvious/true/possible/certain…）+ that 从句  该句型中it 是形式主语，真正的主语是 that 引导的主语从句，常译为 “ 清楚（显然，真的，肯定……）”是主语从句最常见的一种结构。 

It is very clear that he's round and tall like a tree

= That he's round and tall like a tree is very clear

4  It is+形容词（important /necessary/ right/strange/natural）+that 从句(should) do  该句型和上一个同属一个句型。由于主句中的形容词不同，that 后的从句中要用虚拟语气（should + 动词原形），should 可以省去。

It is necessary that we (should)learn a foreign language

当it作主语的句子后面有动词不定式，动名词短语，以及主语从句时，这个it通常是形式主语。如：

It is important to study English It is no use crying over the spilt milk

原意在英语中指代物的第三人称单数。另有其他单词的缩写，例如信息技术：Information Technology；即时翻译 instant translation；创新技术innovative technology等。也指信息技术行业的英文简称。

扩展资料：

it 作形式主语，主要分为下列三种情况：不定式作主语、动名词作主语 和 名词从句作主语。具体分析如下：

不定式作真正主语主要用于下列句型：

1、It + is/was + adj/n (形容词或名词） +to do sth

2、名词作表语。主要有a pity,a pleasure,an idea等。例如：

3、In fact________is a hard job for the police to keep order in an important football match （2001上海高考题）

A this B that

C there D it （答案为D）

参考资料来源：百度百科-it

参考资料来源：百度百科-形式主语

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